Structural Design and Active-Site Modulation of Bifunctional Electrocatalysts and Electrolyte Chemistry for Zinc–Air Batteries

Rechargeable zinc–air batteries (ZABs) have demonstrated considerable potential for commercial application due to their exceptional theoretical energy density, cost-effectiveness, environmental compatibility, and safe reliability. However, their large-scale application is restricted by sluggish kinetics in oxygen evolution (OER) and oxygen reduction (ORR) reactions as well as zinc dendrite formation. Therefore, the exploitation of high-performance electrocatalyst and electrolyte represents a fundamental objective to facilitate reaction kinetics, cycling stability, and charge transfer efficiency. Bifunctional catalysts including precious metal nanoparticles, carbon composites, high-entropy alloys, transition metal compounds, and single-atom catalysts can exhibit tailored electronic structures and bifunctional reactivity for both ORR/OER processes. The rational design of these catalysts can provide new avenues for optimizing their fine structure and enhancing catalytic activity. The well-known design principles for electrocatalytic materials such as d-band center theory, spin-state optimization, orbital hybridization, and magnetic field-assisted charge redistribution can provide effective guidelines to optimize adsorption energetics and accelerate reaction dynamics. Herein, this review summarizes the state-of-the-art electrocatalyst design strategies, and elucidates the structure-activity relationships from theoretical and experimental insights. Optimization schemes for efficient electrolytes are explored, aiming to offer valuable guidance and profound understanding for developing highly efficient Zn–air batteries.